Functionalized porous materials and applications in medical devices

ABSTRACT

The invention relates to porous polymeric materials, methods of making them, and applications in medical devices. A specific embodiment of the invention encompasses a material comprising a porous polyolefin substrate containing inclusions of a material to which chemical or biological moieties are attached directly or via a spacer.

1. FIELD OF THE INVENTION

The invention relates to porous polymeric materials to which chemical orbiological moieties have been attached, and methods for making the same.

2. BACKGROUND OF THE INVENTION

Porous polymeric materials can be used in a variety of applications.Their uses include medical devices that serve as substitute bloodvessels, synthetic and intraocular lenses, electrodes, catheters, andextracorporeal devices such as those that are connected to the body toassist in surgery or dialysis. Porous polymeric materials can also beused as filters for the separation of blood into component blood cellsand plasma, microfilters for removal of microorganisms from blood, andcoatings for opthalmic lenses to prevent endothelial damage uponimplantation.

Bonding materials other than polymers to porous polymeric materials canalter the properties of porous polymers. A combination of properties mayprovide porous polymers suitable for the above mentioned purposes. Thiscombination, however, has been difficult to achieve because of thenatural properties of polymers.

The hydrophobic nature of typical polymers, however, has limited theusefulness of porous materials made from them. For example, proteinswill often denature when placed in contact with such materials. Butcontact lenses, implants, and related devices that are in intimatecontact with the body must have hydrophilic surfaces that arebiologically compatible.

The physical and/or chemical properties of a plastic surface can bechanged by adhering or bonding a different material to it. Examples ofthis technique are disclosed by U.S. Pat. No. 4,619,897, which isdirected to a porous resin membrane, and by U.S. Pat. No. 4,973,493,which is directed to a device with a biocompatible surface. Otherexamples of surface modification are provided by U.S. Pat. Nos.5,077,215, 5,183,545, and 5,203,997, which disclose the adsorption ofanionic and nonionic fluorocarbon surfactants onto the surface offluorocarbon support members.

Further examples of surface modification can be found in U.S. Pat. No.5,263,992, which discloses the adsorption of polymeric chains onto asupport member, and in U.S. Pat. No. 5,308,641, which discloses thecovalent attachment of a polyalkylimine to an aminated substrate.

Despite the different techniques available for modifying the surface ofpolymeric materials, most are limited in their ability to control thedegree to which a surface is modified, and many are expensive,inefficient, or cannot be use to modify porous surfaces without coatingor clogging their pores. A need exists for polymeric materials that canalter their functionality depending upon incorporation of additivesand/or post treatment of these additives. The present invention providesnew porous polymeric materials and methods of their manufacture thataddress this need.

3. SUMMARY OF THE INVENTION

This invention encompasses novel porous materials and methods of theirmanufacture. Materials of the invention comprise a porous substrate towhich chemical or biological moieties are bound directly or by a spacer.

A first embodiment of the invention encompasses a material comprising: aporous substrate comprised of a polymer and a functional additive andhaving a surface wherein the surface comprises a region defined by atleast some of the functional additive; and a biological or chemicalmoiety covalently or non-covalently bound to the region. In a preferredmaterial encompassed by this embodiment, the surface comprises aplurality of regions defined by at least some of the functionaladditive, each of which is covalently bound to a chemical or biologicalmoiety.

A second embodiment of the invention encompasses a material comprising:a porous substrate comprised of a polymer and a functional additive andhaving a surface, wherein the surface comprises a region defined by atleast some of the functional additive; a spacer covalently ornon-covalently bound to the region; and a biological or chemical moietycovalently or non-covalently bound to the spacer. In a preferredmaterial encompassed by this embodiment, the surface comprises aplurality of regions defined by at least some of the functionaladditive, each of which is covalently bound a spacer, which in turn isbound to a biological moiety.

Examples of polymers from which materials of the invention can be madeinclude, but are not limited to, polyolefins, polyethers, nylons,polycarbonates, poly(ether sulfones), or mixtures thereof. Polyethersinclude, but are not limited to, polyether ether ketone (PEEK,poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene)),polyether sulfone (PES), or mixtures thereof. Polyolefins include, butare not limited to, ethylene vinyl acetate; ethylene methyl acrylate;polyethylenes; polypropylenes; ethylene-propylene rubbers;ethylene-propylene-diene rubbers; poly(1-butene); polystyrene;poly(2-butene); poly(1-pentene); poly(2-pentene);poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride);poly(tetrafluoroethylene) (PTFE); poly(vinylidene fluoride) (PVDF);acrylonitrile-butadiene-styrene (ABS); or mixtures thereof. Preferredpolyolefins are polyethylene or polypropylene.

Functional additives are materials that contain functional groups suchas, but not limited to, hydroxyl, carboxylic acid, anhydride, acylhalide, alkyl halide, aldehyde, alkene, amide, amine, guanidine,malimide, thiol, sulfonate, sulfonic acid, sulfonyl ester, carbodiimide,ester, cyano, epoxide, proline, disulfide, imidazole, imide, imine,isocyanate, isothiocyanate, nitro, or azide. Preferred functional groupsare hydroxyl, amine, aldehyde, or carboxylic acid. A particularlypreferred functional group is hydroxyl. Examples of functional additivesinclude, but are not limited to, silica powder, silica gel, choppedglass fiber, controlled porous glass (CPG), glass beads, ground glassfiber, glass bubbles, kaolin, alumina oxide, or other inorganic oxides.

Examples of spacers useful in the second embodiment of the inventioninclude, but are not limited to, silanes, functionalized silanes(functional groups such as aldehyde, amino, epoxy, halides, etc.),diamines, alcohols, esters, glycols (such as polyethylene glycol),anhydrides, dialdehydes, terminal difunctionalized polyurethanes,diones, macromer, difunctional and multifunctional polymers with endgroups, including, but not limited to, amino, carboxylic acid, ester,aldehyde, or mixtures thereof. In a preferred material, the spacer towhich the porous substrate and biological or chemical moiety is attachedis of Formula I:

wherein the bond broken by a wavy line are those between the spacer andthe substrate or other moieties; R¹ and R² each independently ishydrogen, substituted or unsubstituted alkyl, aryl, or aralkyl; R³ is asubstituted or unsubstituted aliphatic chain or a bond; and n is aninteger from about 1 to about 18, preferably, n is an integer from about1 to about 10, and more preferably from about 2 to about 5.

A variety of chemical and biological moieties can be attached to theporous substrate or spacer of materials of the invention. Examplesinclude, but are not limited to, drugs (e.g., pharmaceuticals),hydrophilic moieties, catalysts, antibiotics, antibodies, antimycotics,carbohydrates, cytokines, enzymes, glycoproteins, lipids, nucleic acids,nucleotides, oligonucleotides, polynucleotides, proteins, peptides,ligand, cells, ribozymes, or combinations thereof.

A specific material of the invention comprises a porous polyethylenesubstrate having a surface in which a functional additive has beenembedded, and a spacer precursor of Formula II covalently attached to atleast a portion of said functional additive:

wherein R¹, R², and R⁴ each independently is hydrogen, substituted orunsubstituted alkyl, aryl, or aralkyl; R³ is a substituted orunsubstituted aliphatic chain or a bond; X is a group capable of bondingto a biological or chemical moiety, such as OH, NH₂, CHO, CO₂H, NCO,epoxy, and the like, preferably, X is NH₂ or CHO; and n is an integerfrom about 1 to about 18, preferably, n is an integer from about 1 toabout 10, and more preferably from about 2 to about 5.

Still another specific material of the invention comprises a porouspolyethylene substrate having a surface in which a functional additivehas been embedded, and a spacer of Formula I covalently attached to atleast a portion of said functional additive and to a chemical orbiological moiety. Preferably, the chemical or biological moiety is anucleotide, oligonucleotide, polynucleotide, peptide, cell, ligand, orprotein.

A third embodiment of the invention encompasses a method of providing amaterial which comprises: forming a porous substrate comprised of apolymer and a functional additive and having a surface, wherein thesurface comprises a region defined by at least some of the functionaladditive, wherein the region contains at least one functional group;contacting the functional group with a spacer under reaction conditionssuitable for the formation of a covalent bond between an atom of thefunctional group arid an atom of the spacer; and contacting the spacerwith a chemical or biological moiety under reaction conditions suitablefor the formation of a covalent bond or non-covalent bond between anatom of the spacer and an atom of the chemical or biological moiety.

In a preferred method, the functional group is hydroxyl, carboxylicacid, anhydride, acyl halide, alkyl halide, aldehyde, alkene, amide,amine, guanidine, malimide, thiol, sulfonate, sulfonyl halide, sulfonylester, carbodiimide, ester, cyano, epoxide, proline, disulfide,imidazole, imide, imine, isocyanate, isothiocyanate, nitro, or azide.Preferred functional groups are hydroxyl, amine, aldehyde, andcarboxylic acid.

A fourth embodiment of the invention encompasses a method of providing amaterial which comprises: forming a porous substrate comprised of apolymer and a functional additive and having a surface, wherein thesurface comprises a region defined by at least some of the functionaladditive, wherein the region contains at least one hydroxyl group; andcontacting the hydroxyl group with a compound of Formula II:

wherein R¹, R², R⁴, X, and n are as defined above, under conditionssuitable for the formation of a material of Formula III:

wherein R¹, R², X, and n are as defined above for Formula II; andSurface is the surface of the substrate.

The porous substrate may be formed by at least two methods. In onemethod, beads are sintered together with other polymer beads prior toattaching compounds of Formula II or IV. In another method, compounds ofFormula II or IV are attached to the surface of beads prior to sinteringthe beads to form the porous substrate.

In a specific method of this embodiment, the material of Formula III iscontacted with a chemical or biological moiety having an amine group ifX is an aldehyde or carboxylic acid, or a chemical or biological moietyhaving an aldehyde or carboxylic acid group if X is an amine, underreaction conditions suitable for the formation of a material of FormulaIV:

wherein R¹, R², R³, and n are defined as above for Formula II; R is theporous substrate surface and Moiety is a chemical or biological moiety.

In another specific method of this embodiment, the material of FormulaIV wherein X is NH₂ is contacted with a compound of Formula V:Z-Spacer-Z   Formula Vwherein Spacer is a hydrophilic segment and Z is a terminal groupcapable of covalently or non-covalently bonding to proteins, aminoacids, oligonucleotides, and the like, under reaction conditionssuitable for the formation of a material of Formula VI:

wherein R is the surface of the porous substrate; and R¹, R², and n aredefined as above for Formula II.

Preferably, the Spacer is a hydrophilic polyurethane, polyethyleneglycol, or polyelectrolytes with terminal groups (Z) capable of bondingto proteins, amino acids, oligonucleotides wherein Z includes, but isnot limited to, isocyanurate, aldehydes, amines, carboxylic acids,N-hydroxysuccimide, and the like.

A sixth embodiment of the invention encompasses a method of controllingthe functionalization of a sintered polyolefin substrate whichcomprises: forming a mixture of polyolefin particles and particles of afunctional additive; and sintering the mixture; wherein the functionaladditive comprises functional groups and the concentration of functionaladditive in the mixture is approximately proportional to the density offunctional groups on a surface of the sintered polyolefin substrate. Ina preferred embodiment, the functional additive is silica powder, silicagel, chopped glass fiber, controlled porous glass (CPG), glass beads,ground glass fiber, glass bubbles, kaolin, alumina oxide, or otherinorganic oxides.

3.1. Definitions

As used herein and unless otherwise indicated, the term “alkyl” includessaturated mono- or di-valent hydrocarbon radicals having straight,cyclic or branched moieties, or a combination of the foregoing moieties.An alkyl group can include one or two double or triple bonds. It isunderstood that cyclic alkyl groups comprise at least three carbonatoms.

As used herein and unless otherwise indicated, the term “aralkyl”includes an aryl substituted with an alkyl group or an alkyl substitutedwith an aryl group. An example of aralkyl is the moiety —(CH₂)_(p)Ar,wherein p is an integer of from 1 to about 4, 8, or 10.

As used herein and unless otherwise indicated, the term “aryl” includesan organic radical derived from an aromatic hydrocarbon by removal ofone hydrogen, such as phenyl or naphthyl.

As used herein and unless otherwise indicated, the term “halo” meansfluoro, chloro, bromo, or iodo. Preferred halo groups are fluoro,chloro, or bromo.

As used herein and unless otherwise indicated, the term “non-covalent”when used to describe a bond, means a bond formed by ionic interactions,Van der Waals interactions, hydrogen bonding interactions, stericinteractions, hydrophilic interactions, or hydrophobic interactionsbetween two atoms or molecules.

As used herein and unless otherwise indicated, the term “substituted,”when used to describe a chemical moiety, means that one or more hydrogenatoms of that moiety are replaced with a substituent. Examples ofsubstituents include, but are not limited to, alkyl and halo.

As used herein and unless otherwise indicated, the term “heteroaryl”means an aryl group wherein at least one carbon atom has been replacedwith an O, S, P, Si, or N atom.

As used herein and unless otherwise indicated, the terms “heterocyclicgroup” and “heterocycle” include aromatic and non-aromatic heterocyclicgroups containing one or more heteroatoms each selected from O, S, P,Si, or N. Non-aromatic heterocyclic groups must have at least 3 atoms intheir ring system, but aromatic heterocyclic groups (i.e., heteroarylgroups) must have at least 5 atoms in their ring system. Heterocyclicgroups include benzo-fused ring systems and ring systems substitutedwith one or more oxo moieties. An example of a 3 membered heterocyclicgroup is epoxide, and an example of a 4 membered heterocyclic group isazetidinyl (derived from azetidine). An example of a 5 memberedheterocyclic group is thiazolyl, and an example of a 10 memberedheterocyclic group is quinolinyl. Examples of non-aromatic heterocyclicgroups are pyrrolidinyl, tetrahydrofuranyl, tetrahydrothienyl,tetrahydropyranyl, tetrahydrothiopyranyl, piperidino, morpholino,thiomorpholino, thioxanyl, piperazinyl, azetidinyl, oxetanyl, thietanyl,homopiperidinyl, oxepanyl, thiepanyl, oxazepinyl, diazepinyl,thiazepinyl, 1,2,3,6-tetrahydropyridinyl, 2-pyrrolinyl, 3-pyrrolinyl,indolinyl, 2H-pyranyl, 4H-pyranyl, dioxanyl, 1,3-dioxolanyl,pyrazolinyl, dithianyl, dithiolanyl, dihydropyranyl, dihydrothienyl,dihydrofuranyl, pyrazolidinyl, imidazolinyl, imidazolidinyl,3-azabicyclo[3.1.0]hexanyl, 3-azabicyclo[4.1.0]heptanyl, 3H-indolyl, andquinolizinyl. Examples of aromatic heterocyclic groups are pyridinyl,imidazolyl, pyrimidinyl, pyrazolyl, tiazolyl, pyrazinyl, tetrazolyl,furyl, thienyl; isoxazolyl, thiazolyl, oxazolyl, isothiazolyl, pyrrolyl,quinolinyl, isoquinolinyl, indolyl, benzimidazolyl, benzofuranyl,cinolinyl, indazolyl, indolizinyl, phthalazinyl, pyridazinyl, triazinyl,isoindolyl, pteridinyl, purinyl, oxadiazolyl, thiadiazolyl, furazanyl,benzofurazanyl, benzothiophenyl, benzothiazolyl, benzoxazolyl,quinazolinyl, quinoxalinyl, naphthyridinyl, and furopyridinyl. Theforegoing groups, as derived from the compounds listed above, may beC-attached or N-attached where such attachment is possible. Forinstance, a group derived from pyrrole can be pyrrol-1-yl (N-attached)or pyrrol-3-yl (C-attached).

As used herein, unless otherwise indicated, the term “polyelectrolyte”means a polymer having electronic charges. The polyelectrolyte may existin a complex form, which is also called symplexes. Polyelectrolytes aredivided into polyacids, polybases, and polyampholytes. Depending on thecharge density in the chain, polyelectrolytes are divided into weak andstrong. The charge of weak polyelectrolytes is determined bydissociation constants of ionic groups and pH of the solution. Strongpolyelectrolytes in water solutions are mostly ionized independent ofthe solution's pH. Typical weak polyacid polyelectrolytes include, butare not limited to, poly(acrylic acid) and poly(methacrylic acid).Strong polyacid polyelectrolytes include, but are not limited to,poly(ethylenesulfonic acid), poly(styrenesulfoinic acid), andpoly(phosphoric acid). Weak polybase polyelectrolytes include, but arenot limited to, poly(4-vinylpyridine), polyethyleneimine (PEI), andpolyvinylamine. Strong polybase polyelectrolytes can be obtained byalkylation of nitrogen, sulfur, or phosphorus atoms of weak polybasepolyelectrolytes. See “Concise Polymeric Materials Encyclopedia” (JosephC. Salamone, 1999 by CRC Press LLC, ISBN 0-84932-226-X, pages1140-1141).

3.2. FIGURES

Various aspects of the invention are understood with reference to thefollowing figures:

FIG. 1 represents a side view of a material of the inventions whereinregions of a functional additive are embedded within a porous plasticsubstrate;

FIG. 2 provides a representation of the attachment of spacers of varyinglengths to a porous substrate, followed by the attachment of chemical orbiological moieties to those spacers;

FIG. 3 represents a material of the invention which comprises a spacercovalently bound to a porous substrate, but bound to a chemical orbiological moiety by a non-covalent bond;

FIG. 4 provides a synthetic scheme whereby a chemical or biologicalmoiety can be covalently attached to a porous substrate of the inventionvia an amine-terminated silane spacer;

FIG. 5 provides a synthetic scheme whereby a chemical or biologicalmoiety can be covalently attached to a porous substrate of the inventionvia an aldehyde-terminated silane spacer; and

FIG. 6 provides a synthetic scheme which allows the lengthening of aspacer connecting a porous substrate and a chemical or biologicalmoiety.

4. DETAILED DESCRIPTION OF THE INVENTION

Many plastics do not contain reactive functional groups (e.g., hydroxylor amine groups) that can be used to attach chemical or biologicalmoieties to surfaces of materials made from them. The surfaces of suchmaterials can therefore be difficult to modify. This invention is basedon a discovery that the surface properties of porous plastic materialscan be altered in a controllable fashion by incorporating varyingamounts of functional additives into those materials. Functionaladditives are materials that contain functional groups to whichbiological and/or chemical moieties can be covalently attached.

FIG. 1 depicts various aspects of materials of the invention. Inparticular, it provides a representation of a porous substrate made of aplastic and a functional additive. Portions of the functional additivethat are exposed on the surface of the substrate provide functionalgroups (represented in FIG. 1 as “Fn”) to which chemical or biologicalmoieties (represented by “CBM”) can be covalently bound. Alternatively,a spacer can connect a chemical or biological moiety to the surface.Preferably, the plastic that surrounds the regions of functionaladditives contains few, if any, functional groups. Alternatively, theplastic may contain functional groups that are less reactive undercertain reaction conditions than the functional groups of the functionaladditive, such that chemical or biological moieties can be boundprimarily to exclusively to regions of functional additive.

As discussed elsewhere herein, the polymer (e.g., plastic) from whichthe porous substrate is made is selected to provide a substrate ofdesired strength, flexibility, porosity, and resistance to degradation.Other factors, such as cost and biocompatibility may also play a role inits selection. The chemical or biological moiety(ies) bound to thesubstrate are selected to provide a final material with desired chemicaland/or physical properties, while the type and amount of functionaladditive(s) are selected to affect the number and/or density of chemicalor biological moieties bound to the substrate. For example, the chemicalreactivity of functional groups provided by the functional additive canaffect the number of moieties attached to the substrate surface.

Examples of chemical and/or physical properties conveyed by the covalentbonding of chemical or biological moieties to the surface of a poroussubstrate include, but are not limited to, increased hydrophilicity andbiocompatibility. Indeed, the surfaces of preferred materials of theinvention are hydrophilic, and can readily accept high surface tensionfluids. Examples of high surface tension fluids include, but are notlimited to, water, and aqueous salt and protein solutions. Hydrophilicsubstrates typically have a surface energy of greater than about 40dyn/cm², more typically greater than about 60 dyn/cm².

Materials of the invention can be used in a variety of applications. Forexample, biocompatible materials can be used to provide temporary orpermanent implants such as, but not limited to, soft or hard tissueprosthesis, artificial organs or organ components, or lenses for the eyesuch as contact or intraocular lenses. Biocompatible materials of theinvention reduce or avoid undesirable reactions such as, but not limitedto, blood clotting, tissue death, tumor formation, allergic reaction,foreign body rejection, and inflammation reaction. Preferred implants ofthe invention can be easily fabricated and sterilized, and willsubstantially maintain their physical properties and function during thetime they remain implanted in, or in contact with, tissues andbiological fluids.

Materials of the invention can also be used as, and within, medicaldevices. Examples of medical devices include, but are not limited to,dialysis tubing and membranes, blood oxygenator tubing and membranes,ultrafiltration membranes, diagnostic sensors (e.g., ELISA and sandwichassays), and drug delivery devices.

4.1. Porous Substrates

As shown in FIG. 1, typical materials of the invention comprise a poroussubstrate made of at least one plastic and at least one functionaladditive. The relative amounts and types of plastic(s) and functionaladditive(s) used to provide a substrate depend on the desired properties(e.g., strength, flexibility, and utility) of that material. Forexample, the strength and flexibility of a substrate will typicallyincrease as the amount of functional additive it contains decreases. Butthe number of functional groups on the surface of a substrate willtypically increase as the amount of functional additive it containsincreases, although it is possible to concentration functional additiveat a particular surface of a substrate.

Polymers (e.g., plastics) used to provide typical substrates have few—ifany—functional groups to which chemical, biological, and other moieties(e.g., spacers) can be attached. Typical plastics are hydrophobic, andhave a surface energy of less than about 40 dyn/cm², and more typicallyless than about 30 dyn/cm². Preferred plastics can be easily sintered orotherwise shaped to provide strong, durable, and/or flexible porousmaterials.

Examples of plastics that can be used to provide suitable substratesinclude, but are not limited to, polyolefins, polyethers, nylons,polycarbonates, poly(ether sulfones)., or mixtures thereof. Preferredplastics are polyolefins. Examples of polyethers include, but are notlimited to, polyether ether ketone (PEEK,poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene)),polyether sulfone (PES), or mixtures thereof.

Examples of polyolefins include, but are not limited to, ethylene vinylacetate; ethylene methyl acrylate; polyethylenes; polypropylenes;ethylene-propylene rubbers; ethylene-propylene-diene rubbers;poly(1-butene); polystyrene; poly(2-butene); poly(1-pentene);poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride);poly(tetrafluorcethylene) (PTFE); poly(vinylidene fluoride) (PVDF);acrylonitrile-butadiene-styrene (ABS); or mixtures thereof. Preferredpolyolefins are polyethylene or polypropylene. Examples of suitablepolyethylenes include, but are not limited to, low density polyethylene,linear low density polyethylene, high density polyethylene, ultra-highmolecular weight polyethylene, or derivatives thereof.

Because typical plastics possess no functionality and are hydrophobic,porous substrates made from them according to this invention comprise atleast one type of functional additive. Functional additives arematerials that contain functional groups to which biological and/orchemical moieties can be covalently attached. Examples of functionalgroups include, but are not limited to, hydroxyl, carboxylic acid,anhydride, acyl halide, alkyl halide, aldehyde, alkene, amide, amine,guanidine, malimide, thiol, sulfonate, sulfonyl halide, sulfonyl ester,carbodiimide, ester, cyano, epoxide, proline, disulfide, imidazole,imide, imine, isocyanate, isothiocyanate, nitro, or azide. Preferredfunctional groups are hydroxyl, amine, aldehyde, or carboxylic acid. Aparticularly preferred functional group is hydroxyl.

Mixtures of functional groups can be provided in controlled ratios byincluding two or more additives within a substrate, or by using anadditive that contains more than one type of functional group. Thepresence, types, and densities of functional groups on the surface of asubstrate can be readily determined by methods such astitration, fouriertransform infrared spectroscopy (FTIR), attenuated total reflectance(ATR), and X-ray photoelectron spectroscopy (XPS), or using molecularprobes such as, D-1557 sulfonyl chloride, fluorescein isothiocyanate,fluorescein dichlorotriazine, and the like.

Preferred functional additives are inexpensive, and can be readilyincolporated into porous substrates without degrading (e.g., losingtheir functionality) during the thermal process. Examples of functionaladditives include, but are not limited to, silica powder, silica gel,chopped glass fiber, glass beads, ground glass fiber, or glass bubbles.Preferred functional additives are silica powder or glass fiber, whichprovide hydroxyl functional groups.

Substrates used to provide materials of the invention are porous, andconsequently contain one or more channels through which gas or liquidmolecules can pass. Preferred substrates have an average pore size offrom about 10 μm to about 200 μm, more preferably from about 15 μm toabout 50 μm, and most preferably from about 20 μm to about 30 μm. Meanpore size and pore density can be determined using, for example, amercury porosimeter, or scanning electron microscopy.

Because porous substrates of the invention are made of a porouspolymeric matrix into which inclusions of functional additive aretrapped, a surface of a typical substrate will contain regions offunctional additive surrounded by regions of the polymeric matrix. Thesurface density and size of the regions of functional additive willdepend on a variety of factors, including the desired density ofchemical or biological moieties to be attached to it. In a typicalsubstrate of the invention, functional additive covers about 5% to about60%, and more typically of about 10% to about 50% percent of the surfacearea of the substrate.

4.1.1. Preparation of Porous Substrates

A variety of methods known to those skilled in the art can be used tomake porous substrates. Some examples include sintering; the use ofblowing agents and/or leaching agents; microcell formation methods suchas those disclosed by U.S. Pat. Nos. 4,473,665 and 5,160,674, both ofwhich are incorporated herein by reference; drilling, including laserdrilling; and reverse phase precipitation. Depending on how it is made,a porous substrate can thus contain regular arrangements of channels ofrandom or well-defined diameters and/or randomly situated pores ofvarying shapes and sizes. Pore sizes are typically referred to in termsof their average diameters, even though the pores themselves are notnecessarily spherical.

The particular method used to form the pores or channels of a poroussubstrate and the resulting porosity (i.e., average pore size and poredensity) of the porous substrate can vary according to the desiredapplication to which the final porous material will be put. The desiredporosity of the substrate can also be affected by the substrate materialitself, as porosity can affect in different ways the physical properties(e.g., tensile strength and durability) of different materials.

Preferred substrates of the invention are made by sintering a mixturecomprising particles of at least one polymer (e.g., plastic) andparticles of a functional additive (e.g., silica powder or chopped glassfiber). Optional additional materials such as, but not limited to,lubricants, colorants, and fillers can also be added to the mixture. Therelative amounts of polymer and functional additive depend on thedesired number and density of functional groups on the substrate surfaceand on the desired strength of the final material.

As discussed elsewhere herein, the strength of a substrate may decreaseas its functional additive content increases, although if the functionaladditive can adhere to the plastic surrounding it, this may not be thecase.

The relative amounts of plastic and functional additive used to providea porous substrate will vary with the specific materials used, thedesired functionality of the substrate surface, and the strength andflexibility of the substrate itself. Typically, however, the mixturefrom which the porous substrate is made comprises from about 5% to about60%, more preferably from about 10% to about 40%, and most preferablyfrom about 20% to about 30% weight percent functional additive.

The polymer, functional additive, and optional additional materials areblended to provide a uniform mixture, which is then sintered. Dependingon the desired size and shape of the final product (e.g., a block, tube,cone, cylinder, sheet, or membrane), this can be accomplished using amold, a belt line such as that disclosed by U.S. Pat. No. 3,405,206,which is incorporated herein by reference, or other techniques known tothose skilled in the art. In a preferred embodiment, the mixture issintered in a mold. Suitable molds are commercially available and arewell known to those skilled in the art. Specific examples of moldsinclude, but are not limited to, flat sheets with thickness ranging fromabout ⅛ inch to about 0.5 inch and round cylinders of varying heightsand diameters. Suitable mold materials include, but are not limited to,metals and alloys such as aluminum and stainless steel, high temperaturethermoplastics, and other materials both known in the art and disclosedherein.

In a preferred embodiment, a compression mold is used to provide thesintered material. In this embodiment, the mold is heated to thesintering temperature of the plastic, allowed to equilibrate, and thensubjected to pressure. This pressure typically ranges from about 1 psito about 10 psi, depending on the composition of the mixture beingsintered and the desired porosity of the final product. In general, thegreater the pressure applied to the mold, the smaller the average poresize and the greater the mechanical strength of the final product. Theduration of time during which the pressure is applied also variesdepending on the desired porosity of the final product, and is typicallyfrom about 2 to about 10 minutes, more typically from about 4 to about 6minutes. In another embodiment of the invention, the mixture is sinteredin a mold without the application of pressure.

Once the porous substrate has been formed, the mold is allowed to cool.If pressure has been applied to the mold, the cooling can occur while itis still being applied or after it has been removed. The substrate isthen removed from the mold and optionally processed. Examples ofoptional processing include, but are not limited to, sterilizing,cutting, milling, polishing, encapsulating, and coating.

Using methods such as that described above, a variety of materials ofvarying sizes and shapes can be used to provide a suitable poroussubstrate. In one embodiment, similarly-sized particles of plasticand/or functional additive are sintered. In this embodiment, theparticles' size distribution is preferably narrow (e.g., as determinedusing commercially available screens). This is because it has been foundthat particles of about the same size can be consistently packed intomolds, and because a narrow particle size distribution allows theproduction of a substrate with uniform porosity (i.e., a substratecomprising pores that are evenly distributed throughout it and/or are ofabout the same size). This is advantageous because solutions and gasestend to flow more evenly through uniformly porous materials than thosewhich contain regions of high and low permeability. Uniformly poroussubstrates are also less likely to have structural weak spots thansubstrates which comprise unevenly distributed pores of substantiallydifferent sizes. In view of these benefits, if a polymer is commerciallyavailable in powder (i.e., particulate) form, it is preferably screenedprior to use to ensure a desired average size and size distribution.However, many polymers are not commercially available in powder form.Consequently, methods such as cryogenic grinding and underwaterpelletizing can be used to prepare powders of them.

Cryogenic grinding is a well-known method, which can be used to prepareparticles of plastic and functional additive of varying sizes. Butbecause cryogenic grinding provides little control over the sizes of theparticles it produces, powders made by it may have to be screened toensure that the particles to be sintered are of a desired average sizeand size distribution.

Plastic particles can also be made by underwater pelletizing. Underwaterpelletizing is described, for example, in U.S. patent application Ser.No. 09/064,786, filed Apr. 23, 1998, and U.S. Provisional PatentApplication No. 60/044,238, filed Apr. 24, 1999, both of which areincorporated herein by reference. Although this method is typicallylimited to the production of particles with diameters of at least about36 μM, it offers several advantages. First, underwater pelletizingprovides accurate control over the average size of the particlesproduced, in many cases thereby eliminating the need for an additionalscreening step and reducing the amount of wasted material. A secondadvantage of underwater pelletizing is that it allows significantcontrol over the particles' shape.

Thermoplastic particle formation using underwater pelletizing typicallyrequires an extruder or melt pump, an underwater pelletizer, and adrier. The thermoplastic resin is fed into an extruder or a melt pumpand heated until semi-molten. The semi-molten material is then forcedthrough a die. As the material emerges from the die, at least onerotating blade cuts it into pieces herein referred to as“pre-particles.” The rate of extrusion and the speed of the rotatingblade(s) determine the shape of the particles formed from thepre-particles, while the diameter of the die holes determine theiraverage size. Water, or some other liquid or gas capable of increasingthe rate at which the pre-particles cool, flows over the cuttingblade(s) and through the cutting chamber. This coagulates the cutmaterial (i.e., the pre-particles) into particles, which are thenseparated from the coolant (e.g., water), dried, and expelled into aholding container.

The average size of particles produced by underwater pelletizing can beaccurately controlled and can range from about 0.014″ (35.6 μM) to about0.125″ (318 μM) in diameter, depending upon the porous substrate.Average particle size can be adjusted simply by changing dies, withlarger pore dies yielding proportionally larger particles. The averageshape of the particles can be optimized by manipulating the extrusionrate and the temperature of the water used in the process.

While the characteristics of a porous material can depend on the averagesize and size distribution of the particles used to make it, they canalso be affected by the particles' average shape. Consequently, inanother embodiment of the invention, the particles of plastic andfunctional additive particles are substantially spherical. This shapefacilitates the efficient packing of the particles within a mold.Substantially spherical particles, and in particular those with smoothedges, also tend to sinter evenly over a well defined temperature rangeto provide a final product with desirable mechanical properties andporosity.

In a specific embodiment of the invention, the particles of plasticand/or functional additive are substantially spherical and free of roughedges. Consequently, if the particles used in this preferred method arecommercially available or made by cryogenic grinding, they are thermalfined to ensure smooth edges, and are screened to ensure a properaverage size and size distribution. Thermal fining is a well-knownprocess wherein particles are rapidly mixed and optionally heated suchthat their rough edges become smooth. Mixers suitable for thermal fininginclude the W series high-intensity mixers available from LittlefordDay, Inc., Florence, Ky.

Particles made by underwater pelletizing, which allows precise controlover particle size and can yield smooth, substantially sphericalparticles, typically do not need to be thermal fined or screened.

4.2. Substrate Surface Modification

Once the porous substrate has been formed, chemical and/or biologicalmoieties are bound directly or indirectly to its surface. FIG. 2provides a representation of this process wherein a spacer molecule(e.g., an alkane substituted with at least one functional group) isattached to the surface of a substrate to provide an intermediatematerial. Chemical or biological moieties such as proteins are thenattached to the spacer. Also as shown in FIG. 2, the length of thespacer can be optionally increased by reacting the intermediate materialwith additional chemical moieties to provide a second intermediatematerial, to which chemical or biological moieties can be attached.

As used herein, spacers are differentiated from chemical or biologicalmoieties only by their use in a particular instance. To be specific, achemical or biological moiety is something that provides, at least to asubstantial degree, the useful physical or chemical properties of aparticular material. For example, the chemical or biological moiety in amaterial to be used as a biosensor will be a moiety that can recognize,bond, or associate with the molecule(s) to be detected. By contrast, aspacer is a chemical moiety that provides some distance between thesurface of the porous substrate and the chemical or biological moiety.Still, a spacer can augment or facilitate the activity or utility of achemical or biological moiety by removing it from the surface of thesubstrate. It will be readily apparent to those of skill in the art,however, that a moiety used as a spacer in one instance can be thechemical or biological moiety in another.

Spacers and biological or chemical moieties that are directly bound tothe substrate surface are bound covalently or though strong multi-pointnon-covalent interactions. However, bonds between moieties bound to thesurface and other moieties not bound to the surface need not becovalent. For example, FIG. 3 represents a material comprised of aspacer covalently attached to a porous substrate, wherein the spacer canform ligand-receptor or hybridization-type bonding with apharmacologically active chemical or biological moiety. In a specificexample of a material encompassed by the representation of FIG. 3, thespacer is an oligonucleotide, and the chemical or biological moietycomprises an oligonucleotide or polynucleotide complementary to thespacer.

The invention further encompasses spacers that are capable ofselectively releasing an immobilized chemical or biological moiety. Forexample, a drug may be attached to a spacer by a bond that readilyhydrolyzes under physiological conditions, or which breaks when exposedto radiation of a particular energy. Such materials can be useful forthe controlled release of drugs.

In order to form a covalent bond between the substrate surface and amoiety, a functional group on the surface must be complementary to afunctional group on the chemical precursor of the moiety. In otherwords, functional groups on the surface and on the precursor to whateverwill be attached to it must be capable of forming a covalent bond undersuitable reaction conditions. An example of complementary groups isamine and aldehyde, which can react to form a bond under suitableconditions. Other complementary pairs of functional groups will bereadily apparent to those skilled in the art.

Examples of spacers include, but are not limited to, silanes, silanealdehydes, diamines, alcohols, esters, glycols (such as polyethyleneglycol), anhydrides, dialdehydes, terminal difunctionalizedpolyurethanes, succinic acid, diaminohexanes, glyoxylic acids, glycines,dentrimers, multifunctional polymers, and diones. Preferred spacers arethose of Formula I:

wherein the bond broken by a wavy line are those between the spacer andthe substrate or other moieties; R¹ and R² each independently ishydrogen, substituted or unsubstituted alkyl, aryl, or aralkyl; R³ is asubstituted or unsubstituted aliphatic chain or a bond; and n is aninteger from about 1 to about 18, preferably n is an integer from about1 to about 10, and more preferably n is about 2 to about 5. Morepreferred spacers are those of Formula VIII:

wherein R¹, R², and n are as defined above; R is the surface of theporous substrate; X is a group capable of bonding to a biological orchemical moiety, such as OH, NH₂, CHO, CO₂H, NCO, epoxy, and the like; mis an integer from about 1 to about 5; o is an integer from 0 to about3; most preferably, X is NH₂ or CHO.Other more preferred spacers are those of Formula IX:

wherein R, R¹, R², and n are as defined above.

A wide array of chemical and biological moieties can be attacheddirectly or via a spacer to the surface of a porous substrate. Examplesof such moieties include, but are not limited to, drugs (e.g.,pharmaceuticals), hydrophilic moieties, catalysts, antibiotics,antibodies, antimycotics, carbohydrates, cytokines, enzymes,glycoproteins, lipids, nucleic acids, nucleotides, oligonucleotides,peptides, polynucleotides, proteins, cells, ligands, ribozymes, orcombinations thereof.

4.2.1. Functionalization of Substrates

A porous substrate is functionalized according to the invention by thecovalent bonding of a molecule (e.g., a spacer or chemical or biologicalmoiety) to its surface. The molecule can often be directly attached tothe surface of the substrate. However, it is sometimes desirable toattach a chemical or biological moiety to a substrate indirectly bymeans of a spacer.

For example, if a biological moiety is to interact with molecules insolution, it may interact with such molecules more readily if positionedat some distance from the surface to which it is attached.Alternatively, the shape and size of some biological moieties canprevent the formation of covalent bonds between them and functionalgroups on a substrate surface. In such cases, a spacer is used to linkthe moiety to the surface.

FIG. 4 illustrates a method by which amine-functionalized chemical orbiological moieties can be attached to the surface of a substrate of theinvention. In this method, a silane with a terminal amine reacts with ahydroxyl group provided by a functional additive such as silica powderembedded in the surface. The terminal amine of the resulting materialcan then be converted to an aldehyde using, for example, an excess ofglutaraldehyde. The resulting product is then contacted with anamine-functionalized chemical or biological moiety (e.g., a protein) theunder suitable conditions to form a material of the invention. FIG. 5shows a related method, wherein the silane initially reacted with thesubstrate surface already has a terminal aldehyde, which can react withamine-functionalized chemical or biological moieties.

In some cases, a spacer such as that shown in FIG. 4 and FIG. 5 is ofinsufficient length to provide a useful material, i.e., a desirableenvironment for the bioactive substance. In such cases, the length ofthe spacer can be increased using methods readily apparent to thoseskilled in the art. One example is shown in FIG. 6. According to thismethod, a silane with a terminal amine reacts with a hydroxyl groupprovided by a functional additive such as silica powder embedded in thesurface. The resulting material is then contacted under suitableconditions with a compound of Formula VI:Z-Spacer-Z   Formula VIwherein Spacer is a hydrophilic segment and Z is a terminal groupcapable of covalently or non-covalently bonding to proteins, aminoacids, oligonucleotides, and the like. Preferably, Spacer is hydrophilicpolyurethane, polyethylene glycol, or polyelectrolytes with terminalgroups (Z) capable of bonding to proteins, amino acids, oligonucleotideswherein Z includes, but is not limited to, isocyanurate, aldehydes,amino, carboxylic acids, N-hydroxysuccimide, and the like. In a morepreferred compound of Formula VI, Spacer is hydrophilic polyurethane(NCO-hydrophilic polyurethane-NCO) orN-hydroxysuccimide-PEG-N-hydroxysuccimide (PEG-NHS). The resultingcomplex is then contacted with an amine-functionalized chemical orbiological moiety under reaction conditions suitable for the formationof a covalent bond.

5. EXAMPLES

Certain embodiments of the invention, as well as certain novel andunexpected advantages of the invention, are illustrated by the followingnon-limiting examples. Materials were purchased from Sigma-Aldrich Co.(Milwaukee, Wis.).

5.1 Example 1 Preparation of a Hydrophilic Polyurethane Spacer

A reaction flask was charged under nitrogen with4,4′-methylenebis(cyclohexyl isocyanate) (5.8 g), dibutyltin bis(ethylhexanoate) (30 mg), and THF (10 g). Using a heating mantle, the reactionflask was gently warmed to 65° C. Subsequently, a solution ofpolyethylene glycol (PEG 1000) (MW=1000, 11.2 g) dissolved in 25 g ofTHF was added dropwise to the reaction flask. After the addition wascomplete, the reaction was allowed to proceed for 12 hours at 65° C.under nitrogen. The resulting solution, a light-yellow and transparentgel, was poured out of the reaction flask and stored in a sealed glassbottle filled with dry nitrogen.

5.2 Example 2 Preparation of a Porous Plastic with Glass Powder asDopant

Glass bubble (amorphous silica, CAS No. 7631-86-9) supplied by 3M (St.Paul, Minn.) was blended with an ultra high molecular weightpolyethylene powder GUR 2122 by TICONA (Summit, N.J.) at 20% by weight.After tne mixture was well blended, it was placed into a 0.25 inch flatmold. Using an electrically heated plate, the mold was heated to and waskept at 140° C. for 4 minutes. A skilled artisan can readily determinethe amount of time to heat the mold, depending upon the thickness of thefinal product. After heating, the mold was cooled and the porous plasticwith immobilized glass bubbled was removed.

5.3 Example 3 Preparation of a Functionalized Porous Material (Method 1)

Binding buffer (10 mM phosphate; pH 7.5, 0.015 M NaCl). 0.192 gNaH₂PO_(4, 2.252) g Na₂HPO₄.7H₂O and 0.27 g of NaCl are dissolved in 800ml deionized (DI) water. The pH 7.5 is adjusted with 1N HCl/1N NaOH, andthe volume is brought to 1000 ml with DI water. The buffer is thenpurged with nitrogen before coupling procedure.

Washing buffer: (10 mM phosphate, pH 7.5, 1.0 M NaCl). 5.844 g NaCl isdissolved in 100 ml of binding buffer.

Storage buffer: (10 mM phosphate, pH 7.5, 0.15M NaCl, 0.02% NaN₃).

Silica powder incorporated substrate, prepared in Example 2, is washedwith alcohol, filtered, and air dried. After the substrate has beencompletely dried, they are immersed into a silane solution (5% of3-aminopropyltriethoxysilane/isopropanol solution, CAS #: 919-30-2)until the substrate is completely wet. The substrate is removed from thesolution and air dried. After the substrate is half-dried, it is placedinto an oven at about 60 to 70° C. for about 30 minutes. After thesubstrate is completely dried it is submerged in aglutaraldehyde/alcohol solution (20%) for about 20 minutes. Thesubstrate is dried again in the oven for 30 minutes. Finally, thereactive substrate is dipped into protein/binding buffer solution (0.1mg/ml IgG solution) and mixed gently for 24 hours at 4° C. The bindingbuffer of unreacted protein solution is drained from the matrix. Thefunctionalized porous material is then immersed in a washing buffer (pH7.5), and sodium cyanoborohydride is added until the final concentrationis approximately 1.0 M. The functionalized porous material is washedwith washing buffer (pH 7.5) until all excess sodium cyanoborohydride isremoved and immersed in storage buffer at 4° C.

5.4 Example 4 Preparation of a Functionalized Porous Material (Method 2)

The silica powder incorporated substrate, prepared in Example 2) iswashed and dried as described above. The substrate is immersed into asilane solution (5% of aldehyde trimethoxysilane/isopropanol solution)until the substrate is completely wet. Aldehyde methoxysilane wassupplied by United Chemical Corporation, Piru, Calif. The substrate isfiltered out of the solution and rinsed with anhydrous isopropanol. Thesubstrate is then air dried. After the substrate is half-dried, thesubstrate is placed in an oven at about 60° C. to 70° C. for 30 minutes.The reactive substrate is dipped into protein/binding buffer solution(0.1 mg/ml IgG solution) and mixed gently for 24 hours at 4° C. Thebinding buffer of unreacted protein solution is drained, and thesubstrate is immersed in washing buffer (pH 7.5). Sodiumcyanoborohydride is added until the final concentration is approximately1.0 M. The functionalized porous material is then washed with washingbuffer (pH 7.5) until all excess sodium cyanoborohydride is removed andimmersed in storage buffer at 4° C.

5.5 Example 5 Preparation of a Functionalized Porous Material (Method 3)

In a separate procedure, the silica powder incorporated substrate iswashed with alcohol, filtered, and air dried. After the substrate hasbeen completely dried, it is immersed into a silane solution (5% of3-aminopropyltriethoxysilane/isopropanol solution, CAS #: 919-30-2)until completely wet. The substrate is filtered out of the solution andair dried. The substrate is half-dried and placed in an oven at about 60to 70° C. for 30 minutes. After the substrate is completely dried it issubmerged into hydrophilic polyurethane/tetra-hydrofuran (THF) solutionfor about 6 hours. The preparation of the hydrophilic polyurethane wasdescribed in Example 5.1. The synthesis of other suitable hydrophilicpolyurethanes was described in U.S. patent application Ser. No.09/375,383, which is incorporated herein by reference. The substrate isthen filtered out of the solution and rinsed with dry THF. The washedsubstrate is then dried in a vacuum oven to drive off the residual THF.Finally, the reactive substrate is dipped into a protein/binding buffersolution (0.1 mg/ml IgG solution) and mixed gently for 24 hours at 4° C.The binding buffer of unreacted protein solution is drained, and thesubstrate is immersed in washing buffer (pH 7.5). Sodiumcyanoborohydride is added until the final concentration is approximately1.0. The functionalized porous material is washed with washing buffer(pH 7.5) until all excess sodium cyanoborohydride is removed andimmersed in storage buffer at 4° C.

5.6. Example 6 Detection of Functional Groups

The hydroxyl functionality of the substrate can be characterized inseveral ways.

For example, X-ray photoelectron spectroscopy (XPS) can offer theelemental information about oxygen. Also, Fourier Transform Infra-redSprectroscopy (FTIR) can reveal certain chemical structures, such ashydroxyl. Direct measurement of surface R—OH concentrations can becarried out by using the molecular probe D-1557 sulfonyl chloride fromMolecular Probes Inc., of Eugene, Oreg. after reaction of the basehydrolysis (which releases the chromophore) of the sulfonic acid esterformed by reaction of the D-1557 probe (1 mg/ml in cry acetone with 1.0%pyridine) of the hydroxyl functionalized polymer surface.

Detection of amine groups can be carried out in several ways. Amineselective molecular probes such as fluorescein isothiocyanate (FITC) andfluorescein dichlorotriazine (DTAF) react with all functionalizedsurfaces throughout the porous polyethylene article, while beingunreactive with the unmodified surfaces. Cleavage of the isothioureaformed by reaction of FITC with alkyl amine functions with aqueous 0.1 MNaOH releases fluorescein into solution for direct spectrophotometricmeasurement and the number of nicromoles of amine function per gram ofporous solid can be calculated. The amino groups on an aminated specimencan also be determined chemically according to R. Allul (DNA Probes, H.G. Keller et al. eds., Macmillan, N.Y. (1993)). Thus, the aminatedspecimen is treated with3-O-4-(nitrophenylsuccinylated)-5′-O-DMT-deoxyribonucleoside, followedby blockage of unreached amines with pyridine/acetic anhydride/N-methylimidazole (8:1:1, v:v:v). The amount of bound deoxyribonucleoside isdetermined by absorbance at 498 nm after treatment with 70% aqueousperchloric acid, toluenesulfonic acid in acetonitrile, commercialdeblock preparations, or the like, to release the DMT group from thesupport.

Another method for the detection of amino functional groups is carriedout as follows. Amino functional porous plastics (1 g) cut into 1 mmparticles are mixed with a 0.2 mM Sulfo-SDTB solution, made bydissolving 3 mg of Sulfo-SDTB into 25 ml 0.025 M NaHCO₃ buffer solution(pH 8.5) at room temperature for one hour. Remove the porous plasticsand rinse three times with 15 ml of deionized water for 10 min. Add therinsed porous plastics to 10 ml of 50% perchloric acid water solutionand shake at room temperature for 15 min. Remove a 3 ml sample andmeasure the absorbency at a 498 nm wavelength with a 1 cm path length UVcuvette. The amino functional group density can be calculated by C(Mamino group/gram porous plastic)=3.3(As-Af)/70000.

It should be understood that variations and modifications within thespirit and scope of the invention may occur to those skilled in the artto which the invention pertains. Accordingly, all expedientmodifications readily attainable by one versed in the art from thedisclosure set forth herein that are within the scope and spirit of theinvention are to be included as further embodiments of the invention.The scope of the invention accordingly is to be defined as set forth inthe appended claims.

1. A material comprising: a porous substrate comprised of a polymer anda functional additive and having a surface, wherein the surfacecomprises a region defined by at least some of the functional additive;and a biological or chemical moiety covalently or non-covalently boundto the region.
 2. The material of claim 1, wherein the surface comprisesa plurality of regions defined by at least some of the functionaladditive, each of which is covalently or non-covalently bound to achemical or biological moiety.
 3. A material comprising: a poroussubstrate comprised of a polymer and a functional additive and having asurface, wherein the surface comprises a region defined by at least someof the functional additive; a spacer covalently bound to the region; anda biological or chemical moiety covalently or non-covalently bound tothe spacer.
 4. The material of claim 3, wherein the surface comprises aplurality of regions defined by at least some of the functionaladditive, each of which is covalently bound to a spacer, which in turnis covalently or non-covalently bound to a biological moiety.
 5. Thematerial of claim 1 or 3, wherein the polymer is a polyolefin,polyether, nylon, polycarbonate, poly(ether sulfone), or a mixturethereof.
 6. The material of claim 5, wherein the polyolefin is ethylenevinyl acetate; ethylene methyl acrylate; polyethylenes; polypropylenes;ethylene-propylene rubbers; ethylene-propylene-diene rubbers;poly(1-butene); polystyrene; poly(2-butene); poly(1-pentene);poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride);poly(tetrafluoroethylene) (PTFE); poly(vinylidene fluoride) (PVDF);acrylonitrile-butadiene-styrene (ABS); or a mixture thereof.
 7. Thematerial of claim 5, wherein the polyolefin is polyethylene orpolypropylene.
 8. The material of claim 5, wherein the polyether ispolyether ether ketone (PEEK,poly(oxy-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene)),polyether sulfone (PES), or a mixture thereof.
 9. The material of claim1 or 3, wherein the functional additive comprises a hydroxyl, carboxylicacid, anhydride, acyl halide, alkyl halide, aldehyde, alkene, amide,amine, guanidine, malimide, thiol, sulfonate, sulfonic acid, sulfonylester, carbodiimide, ester, cyano, epoxide, proline, disulfide,imidazole, imide, imine, isocyanate, isothiocyanate, nitro, or azidefunctional group.
 10. The material of claim 9, wherein the functionaladditive comprises a hydroxyl, amine, aldehyde, or carboxylic acidfunctional group.
 11. The material of claim 10, wherein the functionaladditive comprises a hydroxyl functional group.
 12. The material ofclaim 1 or 3, wherein the functional additive is silica powder, silicagel, chopped glass fiber, controlled porous glass (CPG), glass beads,ground glass fiber, glass bubbles, kaolin, alumina oxide, or a mixturethereof.
 13. The material of claim 3, wherein the spacer is a silane,functionalized silane, diamine, alcohol, ester, glycol, anhydride,dialdehyde, terminal difunctionalized polyurethane, dione, macromer, ora multifunctional polymer.
 14. The material of claim 1, wherein thespacer to which the porous substrate and biological or chemical moietyis attached is of Formula I:

wherein the substrate is bound to the oxygen atom and the chemical orbiological moiety is bound to R³; R and R′ each independently ishydrogen, substituted or unsubstituted alkyl, aryl, or aralkyl; R³ is asubstituted or unsubstituted aliphatic chain or a bond; and n is aninteger from about 1 to about
 18. 15. The material of claim 1 or 3,wherein the chemical or biological moiety is a drug, hydrophilic moiety,catalyst, antibiotic, antibody, antimycotic, carbohydrate, cytokine,enzyme, glycoprotein, lipid, nucleic acid, nucleotide, oligonucleotide,peptide, protein, ligand, cell, ribozyme, or a combination thereof. 16.A material comprising a porous polyethylene substrate having a surfacein which a functional additive has been embedded, and a spacer precursorof Formula II covalently attached to at least a portion of saidfunctional additive:

wherein R¹, R² and R⁴ each independently is hydrogen, substituted orunsubstituted alkyl, aryl, or aralkyl; R³ is a substituted orunsubstituted aliphatic chain or a bond; n is an integer from about 1 toabout 18; and X is OH, NH₂, CHO, CO₂H, NCO or epoxy.
 17. A materialcomprising a porous polyethylene substrate having a surface in which afunctional additive has been embedded, and a spacer of Formula I:

wherein R and R′ each independently is hydrogen, substituted orunsubstituted alkyl, aryl, or aralkyl; R³ is a substituted orunsubstituted aliphatic chain or a bond; and n is an integer from about1 to about 18, covalently attached to at least a portion of saidfunctional additive and to a chemical or biological moiety.
 18. Thematerial of claim 17, wherein the chemical or biological moiety is anucleotide, oligonucleotide, polynucleotide, peptide, cell, ligand, orprotein.
 19. A method of providing a material which comprises: forming aporous substrate comprised of a polymer and a functional additive andhaving a surface, wherein the surface comprises a region defined by atleast some of the functional additive, wherein the region contains atleast one functional group; contacting the functional group with aspacer under reaction conditions suitable for the formation of acovalent bond between an atom of the functional group and an atom of thespacer; and contacting the spacer with a chemical or biological moietyunder reaction conditions suitable for the formation of a covalent ornon-covalent bond between an atom of the spacer and an atom of thechemical or biological moiety.
 20. The method of claim 19, wherein thefunctional group is hydroxyl, carboxylic acid, anhydride, acyl halide,alkyl halide, aldehyde, alkene, amide, amine, guanidine, malimide,thiol, sulfonate, sulfonic acid, sulfonyl ester, carbodiimide, ester,cyano, epoxide, proline, disulfide, imidazole, imide, imine, isocyanate,isothiocyanate, nitro, or azide.
 21. The method of claim 19, wherein theporous substrate is formed by sintering beads and then attaching thespacer, or attaching the spacer to beads prior to sintering the beads.22. A method of providing a material which comprises: forming a poroussubstrate comprised of a polymer and a functional additive and having asurface, wherein the surface comprises a region defined by at least someof the functional additive, wherein the region contains at least onehydroxyl group; and contacting the hydroxyl group with a compound ofFormula II:

wherein each of R¹, R², and R⁴ each independently is hydrogen,substituted or unsubstituted alkyl, aryl, or aralkyl; R³ is asubstituted or unsubstituted aliphatic chain or a bond; n is an integerfrom about 1 to about 18; and X is OH, NH₂, CHO, CO₂H, NCO, or epoxyunder conditions suitable for the formation of a material of Formula m:

wherein Surface is the surface of the porous substrate.
 23. The methodof claim 22 wherein the material of Formula III is contacted with achemical or biological moiety having an amine group if X is an aldehydeor carboxylic acid, or a chemical or biological moiety having analdehyde of carboxylic acid group if X is an amine, under reactionconditions suitable for the formation of a material of Formula V:

wherein Moiety is the chemical or biological moiety.
 24. The method ofclaim 22 wherein the material of Formula III, X is NH₂ and is contactedwith a compound of Formula V:Z-Spacer-Z   Formula V wherein Spacer is a hydrophilic segment and Z isa terminal group capable of covalently or non-covalently bonding toproteins, amino acids, oligonucleotides, under reaction conditionssuitable for the formation of a material of Formula VI:

wherein R is the surface of the porous substrate.
 25. The method ofclaim 24, wherein Spacer is a hydrophilic polyurethane, polyethyleneglycol, or polyelectrolyte and wherein Z is isocyanurate, aldehyde,amino, carboxylic acid, or N-hydroxysuccimide.
 26. A method ofcontrolling the functionalization of a sintered polyolefin substratewhich comprises: forming a mixture of polyolefin particles and particlesof a functional additive; and sintering the mixture; wherein thefunctional additive comprises functional groups and the concentration offunctional additive in the mixture is approximately proportional to thedensity of functional groups on a surface of the sintered polyolefinsubstrate.
 27. The method of claim 26, wherein the functional additiveis silica powder, silica gel, chopped glass fiber, controlled porousglass (CPG), glass beads, ground glass fiber, glass bubbles, kaolin,alumina oxide, or a mixture thereof.
 28. The material of claim 13wherein the spacer to which the porous substrate and biological orchemical moiety is attached is of Formula VIII:

wherein R is the surface of the porous substrate; R¹ and R² eachindependently is hydrogen, substituted or unsubstituted alkyl, aryl, oraralkyl; X is OH, NH₂, CHO, CO₂H. NCO, or epoxy; n is an integer fromabout 1 to about 5; m is an integer from about 2 to about 5; and o is aninteger from 0 to about
 3. 29. The material of claim 25 wherein X is CHOor NH₂.
 30. The material of claim 13 wherein the spacer to which theporous substrate and biological or chemical moiety is attached is ofFormula IX:

wherein R is the surface of the porous substrate; R¹ and R² eachindependently is hydrogen, substituted or unsubstituted alkyl, aryl, oraralkyl; and n is from about 1 to about 18.